Hollow spheres have received much attention in recent years for a variety of technical applications including potential controlled-rate, drug release vehicles; see references 12 to 16 (as cited below).
Some of the hollow nanospheres (˜50-200 nm diameter) have pores on the shell as evidenced by the chemical dissolution of interior materials for hollow particle synthesis. This can allow a passive drug delivery based on slowed-down kinetics. However, there is no convenient, known way of triggered drug release from such nanospheres.
There are many drug delivery mechanisms investigated by previous researchers based on temperature-responsive polymers and hydrogels such as poly(NIPPAm), see references 1 to 5, listed below. However, most of these studies deal with slow release from such polymers or one time temperature change on implanting to human body.